The present invention relates to apparatus and a method for lifting and rotating a large elongate object such as a trailer chassis used to carry intermodal cargo containers during highway transit, about a horizontal axis parallel with the longitudinal axis of the object.
In recent years a growing share of cargos transported by sea or rail are being shipped by intermodal transport. Such cargo is packed by shippers in large rectangular containers which can be carried in specially designed ships, on railroad flat-cars, or on special trailer chassis which are hauled over the highways by truck tractors, as if they were ordinary fixed body semi-trailer cargo vans.
At seaports and major railheads, cargo containers are removed from their respective highway trailer chassis and loaded upon ships or flatcars for ocean or rail transportation, leaving the container chassis empty at least temporarily. Because of the high cost of land in area such as ocean freight terminals and railroad yards, it is highly desirable to minimize the amount of land required for parking empty cargo container chassis. Nevertheless, it is important to have a sufficient number of cargo container chassis conveniently available in such locations to accept and carry cargo containers as they are unloaded from railroad flatcars and, more importantly, from container ships which may carry over 2,000 of such containers.
In the past, heavy-duty fork-lift vehicles and chains have been used to lift and overturn the chassis, so that they may be stacked one upon another, alternatingly upright and upside down. Such inversion and stacking of trailer chassis by the use of forklift vehicles saves land. However, it requires the coordinated efforts of several people and is awkward and dangerous. The practice is also costly, in terms of personnel time and of the damage often experienced by chassis being stacked in such a manner.
Repairs to container chassis frequently require work such as welding to be done from awkward positions when a chassis is located upright in a repair shop, although the repairs could be made much more easily with the chassis on its side or upside down. The difficulty of placing a chassis on its side or upside down, however, has usually been even greater than that of performing the repair work awkwardly.
Efforts have been made previously to provide more convenient storage of cargo trailer chassis. In one storage system, for example, a machine engages the rear end of a container chassis and raises the front end in order to store the chassis in a leaning, nearly vertical position with the front end resting against a large stationary rack, reducing the amount of land required for each individual chassis. The racks of such a system, however, are very expensive, and are difficult to remove.
Another type of apparatus engages the chassis from one side, permitting the chassis to be raised vertically several feet and then rotated about a horizontal axis extending transversely of the chassis, thus rotating the chassis end-for-end. As with standing the trailer chassis nearly vertically, this method and apparatus for inverting the chassis requires a vertical clearance at least as high as the length of the chassis, ordinarily about 40 feet. Additionally, rotating the chassis in this fashion moves the ends of the chassis long distances, and is therefore both awkward and potentially very dangerous.
What has been needed, therefore, is apparatus and a method for more safely, cheaply, and easily inverting and stacking or unstacking cargo container chassis, to facilitate repair work and to permit chassis to be stored in stacks, yet be easily, safely, and quickly unstacked to be used to carry cargo containers as they are unloaded from a ship or railroad train.